The present invention relates to a looper drive for sewing machines, such as chain stitch sewing machines.
A looper drive is known from German Patent Specification No. 877 536 (FIG. 5) corresponding to U.S. Pat. No. 2,704,042. Such a looper drive has a main shaft with a ball eccentric, a spherical shell surrounding the eccentric and a connecting rod connecting the spherical shell to a lever for imparting a rocking motion to a swivel shaft for driving a looper. In this looper drive, the connecting rod has not only the ball joint connection to the main shaft but also a ball joint connection to the lever on the looper drive shaft. At the ball joint connection to the lever, one degree of freedom is eliminated in that a guide lug prevents the connecting rod from rotating. This necessary restriction of the degree of freedom is structurally complicated and leads to kinematic disadvantages. In high-speed chain stitch sewing machines, these kinematic disadvantages show up in the development of considerable noise.